Vacuum Advance problem

[dardal@xxxxxxxxxxxxxxx]

Kerry, advancing timing too far can ruin the idle quality.

Although it does not quite add up (because the symptoms were similar with both 
distributors), there is a chance the centrifugal advance is not working 
properly, and that's why you can advance so much w/out the vacuum advance.  
Here is another thing to check.  Is the car knocking at WOT? (this condition 
should be independent of the vacuum advance, but it depends on the centrifugal 
advance).  If it does, there is a good chance the centrifugal advance is fine, 
and you simply need to retard.  Since you have a timing light, check the 
operation of the centrifugal advance.  As I recall, it advances about 10 
degrees between 1000 and 2000 rpm (on my 2 68's but it is probably about the 
same on the 62).  This is also an easy test, but you need a tach.

Of course, there is a chance the idle mixture can use some enrichnemnt.  When 
the timing is advanced, the demands from the mixture quality increase.  If the 
above does not work, try that.

Also, many vacuum advance modules are adjustable.  Look for a little alen 
wrench.  You may be able to back off on the advance.

D^2
Quoting Kerry Pinkerton <pinkertonk@xxxxxxxxx>:

> This morning I decided to do a quick tuneup and in the process of checking
> the timing, I realized the vacuum advance was not working.  Could not find a
> vacuum advance at any local shop but Autozone had a complete distributor for
> 38 bucks.  Put it in and the car idled great but pingged like mad  Messed
> with advancing and retarding the timing, setting dwell, all the tricks I
> knew.  Nothing worked.  Push the gas and it pings and rattles.  Messing with
> it made it better or worse but nothing made it go away.
> 
> So I called the Doctor. (Robert Soule) who told me the new distributor
> probably had the wrong vacuum advance unit for the car and was over advancing
> the timing.  So what have I done?  Disconnected the vacuum advance and set
> the timing at 16 btdc.  It runs fine but has the same lumpy idle as the old
> distriubutor did.